Colorectal cancer includes cancerous growths in the colon, rectum and appendix. With 655,000 deaths worldwide per year, it is the fourth most common form of cancer in the United States and the third leading cause of cancer-related death in the Western world. Colorectal cancers arise from adenomatous polyps in the colon. These mushroom-shaped growths are usually benign, but some develop into cancer over time. Localized colon cancer is usually diagnosed through colonoscopy. Invasive cancers that are confined within the wall of the colon (TNM stages I and II) are curable with surgery. If untreated, they spread to regional lymph nodes (stage III), where up to 73% are curable by surgery and chemotherapy. Cancer that metastasizes to distant sites (stage IV) is usually not curable, although chemotherapy can extend survival, and in rare cases, surgery and chemotherapy together have seen patients through to a cure (Markowitz and Bertagnolli, 2009, N. Engl. J. Med. 361(25): 2449-60). Radiation is used with rectal cancer.
Breast cancer is a type of cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas, while those originating from lobules are known as lobular carcinomas. While the overwhelming majority of cases occur in women, male breast cancer can also occur.
Worldwide, breast cancer comprises 22.9% of all cancers in women and is more than 100 times more common in women than in men, although men tend to have poorer outcomes due to delays in diagnosis. Prognosis and survival rates for breast cancer vary greatly depending on the cancer type, stage, treatment, and geographical location of the patient. Survival rates in the Western world are high; for example, more than 8 out of 10 women (84%) in England diagnosed with breast cancer survive for at least 5 years. In developing countries, however, survival rates are much poorer.
Many cancers are preceded by adenomas. Adenomas are benign tumours, or neoplasms, of epithelial origin which are derived from glandular tissue or exhibit clearly defined glandular structures. Some adenomas show recognisable tissue elements, such as fibrous tissue (fibroadenomas) and epithelial structure, while others, such as bronchial adenomas, produce active compounds that might give rise to clinical syndromes.
Adenomas may progress to become an invasive neoplasm and are then termed adenocarcinomas. Accordingly, adenocarcinomas are defined as malignant epithelial tumours arising from glandular structures, which are constituent parts of many organs of the body. The term adenocarcinoma is also applied to tumours showing a glandular growth pattern. These tumours may be sub-classified according to the substances that they produce, for example mucus secreting and serous adenocarcinomas, or to the microscopic arrangement of their cells into patterns, for example papillary and follicular adenocarcinomas. These carcinomas may be solid or cystic (cystadenocarcinomas). Each organ may produce tumours showing a variety of histological types, for example the ovary may produce both mucinous and cystadenocarcinoma.
Adenomas in different organs behave differently. In general, the overall chance of carcinoma being present within an adenoma (i.e. a focus of cancer having developed within a benign lesion) is approximately 5%. However, this is related to size of an adenoma. For instance, in the large bowel (colon and rectum specifically) occurrence of a cancer within an adenoma is rare in adenomas of less than 1 centimeter. Such a development is estimated at 40 to 50% in adenomas which are greater than 4 centimeters and show certain histopathological change such as villous change, or high grade dysplasia. Adenomas with higher degrees of dysplasia have a higher incidence of carcinoma. In any given colorectal adenoma, the predictors of the presence of cancer now or the future occurrence of cancer in the organ include size (especially greater than 9 mm) degree of change from tubular to villous morphology, presence of high grade dysplasia and the morphological change described as “serrated adenoma”. In any given individual, the additional features of increasing age, familial occurrence of colorectal adenoma or cancer, male gender or multiplicity of adenomas, predict a future increased risk for cancer in the organ—so-called risk factors for cancer. Except for the presence of adenomas and its size, none of these is objectively defined and all those other than number and size are subject to observer error and to confusion as to precise definition of the feature in question. Because such factors can be difficult to assess and define, their value as predictors of current or future risk for cancer is imprecise.
Once a sporadic adenoma has developed, the chance of a new adenoma occurring is approximately 30% within 26 months.
The symptoms of colorectal cancer depend on the location of tumor in the bowel, and whether is has metastasised. Unfortunately, many of the symptoms may occur in other diseases as well, and hence symptoms may not be conclusively diagnostic of colorectal cancer.
Local symptoms are more likely if the tumor is located closer to the anus. There may be a change in bowel habit (new-onset constipation or diarrhea in the absence of another cause), a feeling of incomplete defecation and reduction in diameter of stools. Tenesmus and change in stool shape are both characteristic of rectal cancer. Lower gastrointestinal bleeding, including the passage of bright red blood in the stool, may indicate colorectal cancer, as may the increased presence of mucus. Melena, black stool with a tarry appearance, normally occurs in upper gastrointestinal bleeding (such as from a duodenal ulcer), but is sometimes encountered in colorectal cancer when the disease is located in the beginning of the large bowl.
A tumor that is large enough to fill the entire lumen of the bowel may cause bowel obstruction. This situation is characterized by constipation, abdominal pain, abdominal distension and vomiting. This occasionally leads to the obstructed and distended bowel perforating and causing peritonitis.
Certain local effects of colorectal cancer occur when the disease has become more advanced. A large tumor is more likely to be noticed on feeling the abdomen, and it may be noticed by a doctor on physical examination. The disease may invade other organs, and may cause blood or air in the urine or vaginal discharge.
If a tumor has caused chronic occult bleeding, iron deficiency anaemia may occur. This may be experienced as fatigue, palpitations and noticed as pallor. Colorectal cancer may also lead to weight loss, generally due to a decreased appetite.
More unusual constitutional symptoms are an unexplained fever and one of several paraneoplastic syndromes. The most common paraneoplastic syndrome is thrombosis, usually deep vein thrombosis.
Colorectal cancer most commonly spreads to the liver. This may go unnoticed, but large deposits in the liver may cause jaundice and abdominal pain (due to stretching of the capsule). If the tumor deposit obstructs the bile duct, the jaundice may be accompanied by other features of biliary obstruction, such as pale stools.
Colorectal cancer can take many years to develop and early detection of colorectal cancer greatly improves the prognosis. Even modest efforts to implement colorectal cancer screening methods can result in a drop in cancer deaths. Despite this, colorectal cancer screening rates remain low. Therefore, screening for the disease is recommended in individuals who are at increased risk. There are currently several different tests available for this purpose:                Digital rectal exam: The doctor inserts a lubricated, gloved finger into the rectum to feel for abnormal areas. It only detects tumors large enough to be felt in the distal part of the rectum but is useful as an initial screening test.        Faecal occult blood test: a test for blood in the stool. Two types of tests can be used for detecting occult blood in stools i.e. guaiac based (chemical test) and immunochemical. The sensitivity of immunochemical testing is superior to that of chemical testing without an unacceptable reduction in specificity (Weitzel J N (December 1999). “Genetic cancer risk assessment. Putting it all together”. Cancer 86 (11 Suppl): 2483-92).        Endoscopy:                    Sigmoidoscopy: A lit probe (sigmoidoscope) is inserted into the rectum and lower colon to check for polyps and other abnormalities.            Colonoscopy: A lit probe called a colonoscope is inserted into the rectum and the entire colon to look for polyps and other abnormalities that may be caused by cancer. A colonoscopy has the advantage that if polyps are found during the procedure they can be removed immediately. Tissue can also be taken for biopsy.                        Double contrast barium enema (DCBE): First, an overnight preparation is taken to cleanse the colon. An enema containing barium sulfate is administered, then air is insufflated into the colon, distending it. The result is a thin layer of barium over the inner lining of the colon which is visible on X-ray films. A cancer or a precancerous polyp can be detected this way. This technique can miss the (less common) flat polyp.        Virtual colonoscopy replaces X-ray films in the double contrast barium enema (above) with a special computed tomography scan and requires special workstation software in order for the radiologist to interpret. This technique is approaching colonoscopy in sensitivity for polyps. However, any polyps found must still be removed by standard colonoscopy.        Standard computed axial tomography is an x-ray method that can be used to determine the degree of spread of cancer, but is not sensitive enough to use for screening. Some cancers are found in CAT scans performed for other reasons.        Blood tests: Measurement of the patient's blood for elevated levels of certain proteins can give an indication of tumor load. In particular, high levels of carcinoembryonic antigen (CEA) in the blood can indicate metastasis of adenocarcinoma. These tests are frequently false positive or false negative, and are not recommended for screening, it can be useful to assess disease recurrence. CA 19-9 and CA 242 biomarkers can indicate e-selectin related metastatic risks, help follow therapeutic progress, and assess disease recurrence. Recently, an assay for detection in plasma of methylated sequences of the Septin 9 gene has also become available to assist in diagnosis of colorectal cancer.        Positron emission tomography (PET) is a 3-dimensional scanning technology where a radioactive sugar is injected into the patient, the sugar collects in tissues with high metabolic activity, and an image is formed by measuring the emission of radiation from the sugar. Because cancer cells often have very high metabolic rates, this can be used to differentiate benign and malignant tumors. PET is not used for screening and does not (yet) have a place in routine workup of colorectal cancer cases.        Whole-body PET imaging is the most accurate diagnostic test for detection of recurrent colorectal cancer, and is a cost-effective way to differentiate resectable from nonresectable disease. A PET scan is indicated whenever a major management decision depends upon accurate evaluation of tumour presence and extent.        Stool DNA testing is an emerging technology in screening for colorectal cancer. Premalignant adenomas and cancers shed DNA markers from their cells which are not degraded during the digestive process and remain stable in the stool. Capture, followed by PCR amplifies the DNA to detectable levels for assay.        High C-Reactive Protein levels as risk marker (http://www.sciencedaily.com/releases/2010/04/100419150831.htm).        
Despite the existence of these tests, diagnosis remains problematic. Most of the more sensitive tests are quite invasive and expensive and therefore uptake by patients is low. There is therefore an ongoing need to develop simpler and more informative diagnostic protocols or aids to diagnosis that enable one to direct colonoscopy at people more likely to have developed adenomas or carcinomas. A simple and accurate screening test would enable much more widely applicable screening systems to be set up. Similarly, with breast cancer there is a significantly better prognosis if the cancer is diagnosed early, this often being difficult to reliably achieve since other than the BRCA gene test as a prognostic indicator of a sub-group of aggressive cancers, reliance still lies primarily with mammograms and self examination to identify tumours, neither technique of which is sensitive enough to reliably detect very early stage cancers.
In work leading up to the present invention it has been determined that changes to the methylation of LOC100526820, in particular two specific regions of LOC100526820, is indicative of the development of neoplasms of the large intestine, such as adenomas and adenocarcinomas. Still further, the identification of specific genomic DNA cytosine nucleotides which become hypermethylated has enabled the development of very simple and specific amplification reactions for routine use in the context of diagnosis.